Vehicular seat belt retractors typically comprise a belt reel rotatably mounted in a frame and ratchet toothing arranged on the frame. Arranged on the belt reel are one or two ratchet pawls which are urged to engage with the ratchet toothing on the frame to activate the blocking mechanism and to block the belt reel non-rotatably. For belt webbing-sensitive activation of the blocking mechanism an inertial disc is mounted on the belt reel rotatable relative thereto. When, due to its mass inertia, the inertial disc trails the rotation of the belt reel it urges by a control cam an actuating shoulder on the ratchet pawl causing the latter to pivot into mesh with the ratchet toothing on the frame.
Geartooth clashing is a problem usually obviated by synchronous meshing. In such a synchronous mesh each or every ratchet pawl is deflected in the direction of the frame only in specific rotary positions of the belt reel so that it can only come into contact with tooth gaps. Synchronizing the blocking mechanism is, however, a complicated procedure.
Also a problem with known blocking mechanisms for belt retractors is wear of the ratchet pawl and ratchet toothing in frequent activation as observed in so-called endurance tests. This wear necessitates use of materials having a correspondingly high load capacity and a generous dimensioning of the components involved.